1. Field of the Invention
This invention relates generally to machine control using global navigation satellite systems (GNSSs) and more particularly to an equipment control system and method.
2. Description of the Related Art
Movable machinery, such as excavators, graders, agricultural equipment, open-pit mining machines, aircraft crop dusters and other mobile operating equipment can benefit from accurate positioning using global navigation satellite systems (GNSSs). For example, U.S. Pat. No. 7,689,354, which is assigned to a common assignee herewith, discloses agricultural equipment equipped with an adaptive guidance system including a multi-antenna GNSS system for guidance, automatic steering, independent implement positioning and spraying control.
In the earth-moving field, a wide variety of equipment has been used for specific applications, such as excavators, backhoes, bulldozers, loaders and motor graders. Earth-moving projects encompass a wide variety of excavating, grading, trenching, boring, scraping, spreading and other tasks, which are performed in connection with road-building, infrastructure improvements, construction, mining and other activities. Such tasks are typically performed by specialized equipment. Such equipment can be relatively sophisticated and can handle relatively high capacities of materials.
Mobile earth-moving equipment is steered and otherwise guided within jobsites. Moreover, the working components of such equipment, such as blades, drills, buckets and ground-engaging tools, are controlled through their various ranges of motion. Machine guidance and control were conventionally accomplished by human operators, who often needed relatively high levels of skill, training and experience for achieving maximum production with the equipment. For example, jobsite grading was typically accomplished by surveying the site, placing stakes at predetermined locations to indicate the locations of “cutting” (i.e. earth removal) and “filling” (i.e. earth placement) operations required to achieve a final grading plan. Cut and fill quantities are preferably balanced as much as possible to avoid added expenses for additional fill material or removing excess material.
In addition to balancing material requirements, design parameters such as water runoff, slope, compaction (relating to load-bearing capacity) and thicknesses of various material layers are important grading and site design criteria. Previous earth-moving machinery tended to be highly reliant on operator skill for achieving desired final results.
The present invention uses satellite positioning systems (SATPSs), such as the Global Positioning System (GPS) and other global navigation satellite systems (GNSSs) for guidance and machine control. Project bidding can thus be based on more precise labor, material quantity, fuel, equipment maintenance, material disposal, time and other cost factors. Project expenses can thus be reduced by controlling input costs of material, material hauling, fuel, labor, equipment utilization, etc. Still further, earth-moving operations that were previously conducted in separate “rough” and “fine” phases can be combined into single-phase procedures due to the greater efficiencies and accuracies achievable with the GNSS machine guidance and control of the present invention. Still further, operators tend to be less fatigued with a relatively high level of automated machine guidance and control, as opposed to manually-intensive control procedures requiring high degrees of concentration and operator interaction.
Various navigation and machine control systems for ground-based vehicles have been employed but each has disadvantages. Systems using Doppler radar encounter errors with the radar and latency. Similarly, gyroscopes, which may provide heading (slew), roll, or pitch measurements, may be deployed as part of an inertial navigation package, but tend to encounter drift errors and biases and still require some external attitude measurements for gyroscope initialization and drift compensation. Gyroscopes have good short-term characteristics but undesirable long-term drift characteristics, especially gyroscopes of lower cost such as those based on a vibrating resonator. Similarly, inertial systems employing gyroscopes and accelerometers have good short-term characteristics but also suffer from drift.
Providing multiple antennas on a vehicle can provide additional benefits by determining an attitude of the vehicle from the GNSS ranging signals received by its antennas, which are constrained on the vehicle at a predetermined spacing. For example, high dynamic roll compensation signals can be output directly to the vehicle steering using GNSS-derived attitude information. Components such as gyroscopes and accelerometers can be eliminated using such techniques. Real-time kinematic (RTK) can be accomplished using relatively economical single frequency L1-only receivers with inputs from at least two antennas mounted in fixed relation on a rover vehicle. Still further, moving baselines can be provided for positioning solutions involving machine components and multi-vehicle/machine GNSS control.
GNSS-based equipment and methods can also be used for machine control, such as earth-moving equipment. GNSS guidance can provide a relatively high level of accuracy. For instance, prior to GNSS guidance and machine control, earth-moving operations tended to rely more on operator skill for manually spot-checking grade elevations in order to smoothly cut and fill a plot of land to a particular height. With the GNSS guidance and machine control of the present invention providing three-dimensional (3D) positional tracking, earth-moving equipment can perform cut, fill, and other earth-moving functions using GNSS positioning data for greater repeatable accuracy and operating efficiencies. Although GNSS-based control techniques have been used in earth-moving machinery, previous GNSS machine control systems used in such equipment do not provide the advantages and features of the present invention.
By using GNSS-equipped earth-moving machines, the need for manual grade checks can be reduced or eliminated on many grading projects. Slope and grade measurements can be obtained with greater accuracy and quality control. Moreover, earth-moving jobs that were previously deemed challenging and complex can be simplified, thus increasing the available pool of qualified earth-moving contractors and equipment operators. GNSS-based guidance and control using the present invention can provide more information and control to the equipment operators, thus enabling them to undertake more difficult tasks than they might have with manually-controlled equipment and techniques. Consistency among operator performance can be improved via GNSS-based automation, resulting in better overall job quality. For example, relatively inexperienced operators can deliver results comparable to those achieved by more experienced operators using the information and automation features of the present invention. Another operator benefit relates to less fatigue, as compared to manually guiding and controlling the equipment and its functions.
Profitability of earth-moving jobs using GNSS-equipped machines tends to improve because bidding and execution risks are more highly controlled, input (e.g., material, material hauling, fuel and labor) costs can be reduced, the necessity of reworking projects in order to meet specifications can be reduced, safety can be improved and equipment can complete more projects between service cycles due to greater operating efficiencies.
Yet another application for GNSS-equipped machines involves snow management, including snow grooming procedures for ski resorts. Maximizing use of available snow, both natural and man-made, is an important aspect of managing winter sports areas, such as ski resorts. Effective snow grooming commonly involves relocating volumes of snow in order to provide sufficient snow base depth, to cover obstacles and for configuring ski runs. Skiers often divert snow while making runs. Resort operators often groom and reconfigure their ski runs after normal operating hours to avoid interfering with daytime recreational activities. At many resorts grooming activities continue through the night.
Snow grooming equipment operators are often exposed to hazardous conditions on the mountain, particularly when operating at night or in bad weather conditions. For example, blizzard conditions are often associated with “white out” conditions restricting visibility. Operating heavy equipment on steep, snow-covered terrain in limited visibility can be hazardous to operators. Also, their procedures commonly require relatively precise navigation and positioning to avoid. Still further, snow base and snow depth control can be difficult without significant experience and terrain knowledge.
Movable machinery, such as agricultural equipment, open-pit mining machines, airplane crop dusters and the like all benefit from accurate global navigation satellite system (GNSS) high precision survey products, and others. However, in existing satellite positioning systems (SATPS) for guided parallel and contour swathing for precision farming, mining, and the like, the actual curvature of terrain may not be taken into account. This results in a less than precise production because of the less than precise parallel or contour swathing. Indeed, in order to provide swaths through a field (in farming, for example), the guidance system collects positions of the vehicle as it moves across the field. When the vehicle commences the next pass through the field, the guidance system offsets the collected positions for the previous pass by the width of the equipment (i.e. swath width). The next set of swath positions is used to provide guidance to the operator as he or she drives the vehicle through the field.
The current vehicle location, as compared to the desired swath location, is provided to the vehicle's operator or to a vehicle's steering system. The SATPS provides the 3-D location of signal reception (for instance, the 3-D location of the antenna). If only 3-D coordinates are collected, the next swath computations assume a flat terrain offset. However, the position of interest is often not the same as where the satellite receiver (SR) is located since the SR is placed in the location for good signal reception, for example, for a tractor towing an implement, an optimal location for the SR may be on top of the cab. However, the position of interest (POI) for providing guidance to the tractor operator may be the position on the ground below the operator. If the tractor is on flat terrain, determining this POI is a simple adjustment to account for the antenna height.
However, if the tractor is on an inclined terrain with a variable tilt, which is often the case, the SATPS alone cannot determine the terrain tilt so the POI also cannot be determined. This results in a guidance error because the POI is approximated by the point of reception (POR), and this approximation worsens as the terrain inclination increases. This results in cross track position excursions relative to the vehicle ground track which would contaminate any attempt to guide to a defined field line or swath. On inclined terrain, this error can be minimized by collecting the vehicle tilt configuration along each current pass or the previous pass. The swath offset thus becomes a vector taking the terrain inclination into account with the assumption that from the first swath to the next one the terrain inclination does not change too much. It can therefore be seen that there is a need for a better navigation/guidance system for use with a ground-based vehicle that measures and takes into account vehicle tilt.
Various navigation systems for ground-based vehicles have been employed but each includes particular disadvantages. Systems using Doppler radar will encounter errors with the radar and latency. Similarly, gyroscopes, which may provide heading, roll, or pitch measurements, may be deployed as part of an inertial navigation package, but tend to encounter drift errors and biases and still require some external attitude measurements for gyroscope initialization and drift compensation. Gyroscopes have good short-term characteristics but undesirable long-term characteristics, especially those gyroscopes of lower cost such as those based on a vibrating resonator. Similarly, inertial systems employing gyroscopes and accelerometers have good short-term characteristics but also suffer from drift. Various systems include navigating utilizing GNSS; however, these systems also exhibit disadvantages. Existing GNSS position computations may include lag times, which may be especially troublesome when, for example, GNSS velocity is used to derive vehicle heading. As a result, the position (or heading) solution provided by a GNSS receiver tells a user where the vehicle was a moment ago, but not in real time. Existing GNSS systems do not provide high quality heading information at slower vehicle speeds. Therefore, what is needed is a low cost sensor system to facilitate vehicle swath navigation that makes use of the desirable behavior of both GNSS and inertial units while eliminating or reducing non-desirable behavior. Specifically, what is needed is a means to employ low-cost gyroscopes (e.g., micro electromechanical (MEM) gyroscopes) which exhibit very good short-term low noise and high accuracy while removing their inherent long-term drift.
Providing multiple antennas on a vehicle can provide additional benefits by determining an attitude of the vehicle from the GNSS ranging signals received by its antennas, which are constrained on the vehicle at a predetermined spacing. For example, high dynamic roll compensation signals can be output directly to the vehicle steering using GNSS-derived attitude information. Components such as gyroscopes and accelerometers can be eliminated using such techniques. Real-time kinematic (RTK) can be accomplished using relatively economical single frequency L1-only receivers with inputs from at least two antennas mounted in fixed relation on a rover vehicle. Still further, moving baselines can be provided for positioning solutions involving tractors and implements and multi-vehicle GNSS control can be provided.
Providing additional antennas in combination with standard SATPS and GNSS guidance, as mentioned above, along with optional gyroscopes is a great method to increase GNSS positioning precision and accuracy, such as is described in U.S. Patent Publication No. 2009/0164067 which is assigned to a common assignee and is incorporated herein. However, accuracy and precision can only improve the efficiency of working vehicles, such as those in the agricultural field, to a limited extent. Although such systems are able to track and guide vehicles in three dimensions, including along ridges and sloped-regions, errors may appear in other aspects of a working vehicle. For example, in an agricultural field-working situation where a tractor is towing an implement, the implement may slide on a sloped-region, or the tractor may list to one side or another when entering softer soil or rocky areas. This can happen repeatedly when a vehicle is guided around the same field, regardless of the precision of the guidance system in pre-planning a path. Thus, a system that can detect such changes in uniformity of a field as the vehicle traverses a path and remember those changes can predict and re-route a more accurate and more economical path than a guidance system alone. Heretofore there has not been available a system and method with the advantages and features of the present invention.
Heretofore there has not been available a GNSS-based guidance and control system for agricultural, earth-moving and other equipment with the advantages and features of the present invention.